Presently known circular woven preforms suffer shortcomings with regard to fiber orientation both in the in-plane and out-of-plane directions. Shortcomings of presently known circular woven preforms can result in low torsional and shear properties in the composite that is ultimately formed from the preform. Also, large complex shapes are difficult to produce with multiaxial constructions presently known in the art, and the process for constructing large complex shapes is not believed to be one step and continuous in the present state of the art.
Several processes have been developed on three-dimensional (3-D) circular weaving. A 3-D circular orthogonal woven preform has been developed using three sets of fibers: circumferential; radial; and axial. This preform disclosed in U.S. Pat. No. 3,993,817 is not a true orthogonal woven preform due to radial fiber placement and is not suitable for continuous and complex sectional preform fabrication.
Another 3-D circular orthogonal woven preform has been developed using three sets of fibers as axial, radial and circumferential and is disclosed in U.S. Pat. No. 4,346,741. The process includes weaving-knitting principles and is suitable for part manufacturing. However, the process is two steps and requires a long set-up time and is labor intensive. Further, it is difficult to arrange directional fiber volume fraction in the preform.
Yet another form of 3-D orthogonal circular woven preform has been developed that is formed from three sets of fibers: axial; circumferential; and radial. The process disclosed in U.S. Pat. No. 4,080,915 includes winding and insertion units. The large dimensional preform can be produced easily, but the process has several steps and requires a pre-stiffened rod for radial reinforcements.